The invention relates generally to an image scanner. More specifically, the present invention relates to an image scanner with sliding elements for holding movable carriage and keeping the same depth of field between scanning module and scanned object.
It is well known to use image scanners to translate the image of a scanned object to a corresponding digital image signal. For getting clearly image, it is important to keep the depth of field between the scanning module and the scanned object in steady during scanning. Especially, it is more important for the scanners using the CIS as the optical elements due to its shorter depth of field.
FIG. 1 is a cross-sectional view of an exiting traditional flatbed scanner. The scanner includes a housing 20 having a scanning plate 22 for holding a scanned object, a lid 10 for pressing the scanned object placed on the scanning plate 22, a sliding rod 31 being parallel to scanning plate 22 in lengthwise direction inside the housing 20, a movable carriage 40, a scanning module (not shown, including a CCD or CIS, a light source, a lens) in the carriage 40 for translating optical image signal to digital signal, and a driving device 32 for driving carriage 40 to move along the sliding rod 31.
According to the scanner shown in FIG. 1, the sliding rod 31 has to be assembled carefully. Then, the distance between the carriage 40 and the scanned object can be certainly kept. However, there are many uncertainties in the manufacture and setting process, so the adjustment becomes difficult. Those make the unsteady distance between carriage 40 and scanned object. Those uncertainties bring the unacceptable quality of scanning image, especially for the scanner with CIS.
The present invention is directed to improve the unsteady distance between the scanning module and the scanned object.
One aspect of the present invention is directed to an improved adjustment and manufacture""s problems caused by having different reference bases of the carriage and the scanned object.
In the present invention, there is a new art disclosed. The scanning plate is the reference base for the scanning module when the carriage is moving. The art provides a plurality of sliding elements which sliding at the both sides of the scanning plate. Then, the carriage is fixed at the sliding elements and sliding with sliding elements. Therefore, the scanning module located at the carriage can stay in a predefined distance from the scanned object when the carriage is moving along the scanning plate. Besides keeping the depth of field between the scanning module and the scanned object, the sliding elements avoid the complex adjustments while assembling the scanner.
The second aspect of the present invention is to reduce the complication of driving mechanism and to easy the assembling. For decreasing the complication of driving mechanism, the present invention is to mount a driving device (e.g. electric motor, gears set etc.) on the carriage and has a rack on the housing. Because one of the gears of the driving device engages with the rack on housing, when the motor is actuated, the carriage is moves along the scanning plate.
A further understanding of the nature and advantages of the invention is realized by reference to the remaining portion of the specification and the drawings.